$(document).ready(function() {
    $('.mainbtn').mouseover(function() {
        $(this).css("color","rgb(255,255,255)");
        $(this).css("background-color", "rgba(0,0,0,0.8)");
    });
    
    $('.mainbtn').mouseleave(function() {
        $(this).css("color","rgb(0,0,0)");
        $(this).css("background-color","rgba(0,0,0,0.1)");
    });
    
    $('#change_image').click(function(e) {
        e.preventDefault();
        $('#captcha').attr("src","php/visual-captcha.php?" + ((new Date()).getTime()));
    });
});